US 6532572 B1 Abstract A method of estimating the number of available transit connections, or porosity, of a hardmac for a logic design routing tool includes the steps of calculating a total metal layer capacity of a hardmac, calculating an absolute porosity of the hardmac from the total metal layer capacity and an internal connection density, and calculating a relative porosity of the hardmac from the total metal layer capacity and the absolute porosity.
Claims(27) 1. A method of estimating porosity of a hardmac comprising the steps of:
(a) calculating a total metal layer capacity of a hardmac;
(b) calculating an absolute porosity of the hardmac from the total metal layer capacity and an internal connection density; and
(c) calculating a relative porosity of the hardmac from the total metal layer capacity and the absolute porosity.
2. The method of
3. The method of
wherein TMLC is the total metal layer capacity, L is a length of the hardmac, and G
_{ROUTING LAYER }is a horizontal grid pitch.4. The method of
PH=K·(TMLC−IRH) wherein PH is the absolute horizontal porosity, K is a coefficient corresponding to average internal routing density, and IRH is a horizontal internal connection density.
5. The method of
(1) partitioning each horizontal routing layer into N vertical zones;
(2) calculating the number of horizontal grids required for internal connections in each of the N vertical zones; and
(3) selecting one of the N vertical zones that requires the greatest number of horizontal grids as the horizontal internal connection density.
7. The method of
8. The method of
wherein TMLC is the total metal layer capacity, W is a width of the hardmac, and G
_{ROUTING LAYER }is a vertical grid pitch.9. The method of
PV=K·(TMLC−IRV) wherein PV is the absolute vertical porosity, K is a coefficient corresponding to average internal routing density, and IRV is a vertical internal connection density.
10. The method of
(1) partitioning each vertical routing layer into M horizontal zones;
(2) calculating the number of vertical grids required for internal connections in each of the M horizontal zones; and
(3) selecting one of the N horizontal zones that requires the greatest number of vertical grids as the vertical internal connection density.
12. The method of
wherein TMLC
_{H }is a total metal layer capacity for horizontal routing metal layers, TMLC_{V }is a total metal layer capacity for vertical routing layers, IRH_{AVE }is an average number of internal connections that cross vertical zones in the horizontal routing layers, and IRV_{AVE }is an average number of internal connections that cross horizontal zones in the vertical routing layers.13. A computer program product for estimating porosity of a hardmac comprising:
a medium for embodying a computer program for input to a computer; and
a computer program embodied in the medium for causing the computer to perform the following functions:
(a) calculating a total metal layer capacity of a hardmac;
(b) calculating an absolute porosity of the hardmac from the total metal layer capacity and an internal connection density; and
(c) calculating a relative porosity of the hardmac from the total metal layer capacity and the absolute porosity.
14. The computer program product of
15. The computer program product of
wherein TMLC is the total metal layer capacity, L is a length of the hardmac, and G
_{ROUTING LAYER }is a horizontal grid pitch.16. The computer program product of
PH=K·(TMLC−IRH) wherein PH is the absolute horizontal porosity, K is a coefficient corresponding to average internal routing density, and IRH is a horizontal internal connection density.
17. The computer program product of
(1) partitioning each horizontal routing layer into N vertical zones;
(2) calculating the number of horizontal grids required for internal connections in each of the N vertical zones; and
(3) selecting one of the N vertical zones that requires the greatest number of horizontal grids as the horizontal internal connection density.
19. The computer program product of
20. The computer program product of
wherein TMLC is the total metal layer capacity, W is a width of the hardmac, and G
_{ROUTING LAYER }is a vertical grid pitch.21. The computer program product of
PV=K·(TMLC−IRV) wherein PV is the absolute vertical porosity, K is a coefficient corresponding to average internal routing density, and IRV is a vertical internal connection density.
22. The computer program product of
(1) partitioning each vertical routing layer into M horizontal zones;
(2) calculating the number of vertical grids required for internal connections in each of the M horizontal zones; and
(3) selecting one of the M horizontal zones that requires the greatest number of vertical grids as the vertical internal connection density.
24. The computer program product of
wherein TMLC
_{H }is a total metal layer capacity for horizontal routing layers, TMLC_{V }is a total metal layer capacity for vertical routing layers, IRH_{AVE }is an average number of internal connections that cross vertical zones in the horizontal routing layers, and IRV_{AVE }is an average number of internal connections that cross horizontal zones in the vertical routing layers.25. A computer program product for estimating porosity of a hardmac comprising:
a medium for embodying a computer program for input to a computer; and
a computer program embodied in the medium for causing the computer to perform the following functions:
(a) calculating a total horizontal metal layer capacity of a hardmac;
(b) calculating a horizontal internal connection density;
(c) calculating an absolute horizontal porosity of the hardmac from the total horizontal metal layer capacity and the horizontal internal connection density;
(d) calculating a relative horizontal porosity of the hardmac from the total horizontal metal layer capacity and the absolute horizontal porosity;
(e) calculating a total vertical metal layer capacity of the hardmac;
(f) calculating a vertical internal connection density;
(g) calculating an absolute vertical porosity of the hardmac from the total vertical metal layer capacity and the vertical internal connection density; and
(h) calculating a relative vertical porosity of the hardmac from the total vertical metal layer capacity and the absolute vertical porosity.
26. The computer program product of
(1) partitioning each horizontal routing layer into N vertical zones;
(2) calculating the number of horizontal grids required for internal connections in each of the N vertical zones; and
(3) selecting one of the N vertical zones that requires the greatest number of horizontal grids as the horizontal internal connection density.
27. The computer program product of
(1) partitioning each vertical routing layer into M horizontal zones;
(2) calculating the number of vertical grids required for internal connections in each of the M horizontal zones; and
(3) selecting one of the M horizontal zones that requires the greatest number of vertical grids as the vertical internal connection density.
Description The present invention relates generally to design tools for integrated circuits. More specifically, but without limitation thereto, the present invention relates to a method for estimating the number of transit connections that may be routed through a hardmac of an integrated circuit. Integrated circuits typically include blocks or partitions of multiple circuit elements called hard macros or “hardmacs”. Each hardmac is a generally rectangular cell that may be a complex hierarchical module containing several smaller modules. Connections made between hardmacs that pass through an intervening hardmac are called transit connections. The number of available transit connections, i.e., the total number of connections of a hardmac minus those connections used internally by the hardmac is termed the porosity of the hardmac. The porosity of each hardmac in an integrated circuit chip design is useful information for logic design tools in designing routable floorplans. Disadvantageously, porosity information is generally not available from hardmac cell libraries, and is generally costly to generate. The present invention advantageously addresses the problems above as well as other problems by providing a method of estimating the number of available transit connections, or porosity, of a hardmac for a logic design routing tool. In one embodiment, the present invention may be characterized as a method of estimating horizontal and vertical porosity of a hardmac that includes the steps of (a) calculating a total metal layer capacity of the hardmac, (b) calculating an absolute porosity of the hardmac from the total metal layer capacity and an internal connection density, and (c) calculating a relative porosity of the hardmac from the total metal layer capacity and the absolute porosity. In another embodiment, the present invention may be characterized as a computer program product for estimating the porosity of a hardmac that includes a medium for embodying a computer program for input to a computer and a computer program embodied in the medium for causing the computer to perform the following functions: (a) calculating a total horizontal metal layer capacity of a hardmac; (b) calculating an absolute horizontal porosity of the hardmac from the total horizontal metal layer capacity and a horizontal internal connection density; (c) calculating a relative horizontal porosity of the hardmac from the total horizontal metal layer capacity and the absolute horizontal porosity; (d) calculating a total vertical metal layer capacity of the hardmac; (e) calculating an absolute vertical porosity of the hardmac from the total vertical metal layer capacity and a vertical internal connection density; and (f) calculating a relative vertical porosity of the hardmac from the total vertical metal layer capacity and the absolute vertical porosity. The above and other aspects, features and advantages of the present invention will be more apparent from the following more specific description thereof, presented in conjunction with the following drawings wherein: FIG. 1 is a diagram of a hardmac floorplan for estimating hardmac porosity according to an embodiment of the present invention; FIG. 2 is a diagram of a hardmac of FIG. 1 illustrating internal connections and transit connections; FIG. 3 is a diagram of a connection tree of the hardmac of FIG. 2; FIG. 4 is a diagram of horizontal metal layers in the hardmac of FIG. 2; FIG. 5 is a diagram of vertical zones within a vertical metal layer of FIG. 4; FIG. 6 is a diagram of vertical metal layers in the hardmac of FIG. 2; FIG. 7 is a diagram of horizontal zones within a vertical metal layer of FIG. 6; and FIGS. 8A, Corresponding reference characters indicate corresponding elements throughout the several views of the drawings. The following description is presented to disclose the currently known best mode for making and using the present invention. The scope of the invention is defined by the claims. A logic design tool called a floorplanning tool is used to lay out an arrangement of circuit modules, or hardmacs, that are connected together to constitute an integrated circuit chip. FIG. 1 is a diagram of a hardmac floorplan FIG. 2 is a diagram illustrating internal connections and horizontal transit connections of the hardmac The hardmac The number of available transit connections FIG. 3 is a diagram of a connection tree of the hardmac The total metal layer capacity for transit connections in the horizontal direction may be defined as the total number of available horizontal grids in metal layers used for routing horizontal connections and may be calculated from the formula: where G FIG. 4 is diagram of horizontal routing layers in the hardmac of FIG. The number of available transit connections
where PH is the absolute horizontal porosity, K is an empirical coefficient corresponding to internal connection density, and IRH is the maximum number of horizontal internal connections crossing a vertical zone of the hardmac The relative horizontal porosity of the hardmac The maximum number of horizontal internal connections crossing a critical zone of the hardmac FIG. 5 is a diagram of vertical zones within a horizontal routing layer of FIG. The different relationships illustrated in FIG. 5 between an internal connection and a vertical zone j determine how many horizontal grids are required in the vertical zone j for each internal connection. The internal connections In a manner similar to that described above, the total metal layer capacity for transit connections in the vertical direction may be defined as the total number of available vertical grids in metal layers used for routing vertical connections: where G FIG. 6 is diagram of vertical routing layers in the hardmac of FIG. The number of available transit connections
where PV is the absolute vertical porosity, K is the empirical coefficient corresponding to internal connection density, and IRV is the maximum number of vertical internal connections crossing a critical zone of th e hardmac The relative vertical porosity of the hardmac The maximum number of vertical internal connections crossing a critical zone of the hardmac FIG. 7 is a diagram of horizontal zones within a vertical routing layer of FIG. The different relationships illustrated in FIG. 7 between an internal connection and a horizontal zone i determine how many vertical grids are required in the horizontal zone i for each internal connection. The internal connections The empirical coefficient K used in formulas (2) and (5) may be calculated from the formula: where TMLC In summary, a method of estimating the porosity of a hardmac includes the steps of calculating a total metal layer capacity of a hardmac, calculating an absolute porosity of the hardmac from the total metal layer capacity and an internal connection density, and calculating a relative porosity of the hardmac from the total metal layer capacity and the absolute porosity. FIGS. 8A, Step In step In step In step In step In step
In step In step In step In step In step In step
In step In step In step Step The flowchart While the invention herein disclosed has been described by means of specific embodiments and applications thereof, other modifications, variations, and arrangements of the present invention may be made in accordance with the above teachings other than as specifically described to practice the invention within the spirit and scope defined by the following claims. Patent Citations
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